Optical fiber splices and connectors, collectively designated hereinafter as "connectors", are necessary components of any optical fiber system. Inasmuch as optical fibers have finite lengths, it is necessary that means be provided for splicing the ends of two such fibers together. Also, where breaks occur, some means, such as a connector, of joining the broken fiber is necessary. In addition, in virtually all optical fiber transmission systems, the fiber or fibers terminate at either active or passive devices to which they must be connected by suitable connections. Such connections also make it possible to rearrange or reroute transmission paths. By "connection" is meant the assembled member which joins and holds the fibers. Such connections usually comprise one or more connector assemblies or sub-assemblies and a clamping or holding means.
Regardless of the nature of the connection, whether splice or connection to a device, the principal criteria for establishing such a connection are that the connector must join two fiber ends with minimum insertion loss and that it must be mechanically stable in the working environment. Low insertion loss depends upon fiber alignment, the optical flatness of the ends of the fibers to be joined, and a minimum gap between the fiber ends. Stability depends primarily upon the mechanical design of the connector, with particular emphasis upon the minimization of thermal effects. In those connectors, where the fibers being joined abut, the mechanical design must maintain the abutting relationship despite application of external forces.
In the prior art, efforts to meet these criteria have often resulted in relatively costly connectors, primarily because of the inclusion of numerous precision machined parts, and often because of undue complexity. Such precision and complexity may be acceptable in trunk lines and central offices, where connector costs represent only a small fraction of the total cost of the installation. On the other hand, in field installations, in which labor costs dominate, the connector cost can be a substantial percentage of the total installation cost and, therefore, is desirably minimized where possible.
The mechanical design of the connector can also affect the cost of its installation, in most cost sensitive applications, such as in the field, i.e., locations remote from a central office, and in short haul data communication, for example. Where the connector is mechanically complex, the installation can be complicated and lengthy, after requiting a high level of skill on the part of the technician. In a field installation, it is desirable that the technician performing the splice or connection be able to do so in a reasonably short time, preferably without the use of special tools, and that such installation not require the exercise of any special skills on the part of the installer.
One prior art connector device that meets, at least to some degree, the aforementioned criteria in a structure that is relatively simple is disclosed in U.S. Pat. No. 4,691,986 of Aberson, Jr. et at. The connector of that patent comprises a pair of contiguous fiber carrying plug members which are supported in an abutting relationship at three or more contact lines along their lengths by elongated alignment rods or by a corrugated alignment sleeve. "Contiguous" plugs are plugs that have been cut from a piece of bored cylindrical stock, the abutting faces in the connector being formed by the cut.
The alignment rods are arranged in a triangular pattern and define a central opening into which the plugs are inserted and slid forward until they abut each other. The assembly thus formed is maintained in the triangular form by a suitable triangular spring clip which applies sufficient compressly force to the assembly to hold the plugs firmly against the support rods and to maintain the abutting relationship of the plugs. The connector requires, for proper alignment of the plugs, three or more support rods or ferrules or a preformed corrugated sleeve. In the case of the support rods, assembly can be somewhat tedious inasmuch as initially there is no support for the support rods themselves to hold them in their proper spaced relationship. In addition, the technician must carry the necessary components with which he assembles a connector, which, in the case of a splice, for example, can number six components. In assembling the connector, the technician pushes the plugs into the ends of the support rod assembly toward the center until the plugs abut. Inasmuch as the butting faces of the plugs, and the fiber contained therein, are precisely ground to a high degree of flatness, it is highly desirable that these faces not be subjected to possible damage. However, damage to the face of a plug, such as chipping, might possibly occur as the plug is pushed into the rod assembly.
A connector similar to the Abetsort, Jr. et al. connector is shown in U.S. Pat. No. 4,545,644 of DeVeau et al., wherein three support rods support two abutting plugs, as in the Aberson, Jr. et al. connector. Two of the alignment rods have curved "flats" thereon which enable the plugs to be closely aligned by rotating each of them on its supporting "flat". The alignment procedure requires means for passing fight through the abutting plugs and measuring the fight scattered at the junction of the fibers in the plugs. Thus, it can be seen that the installer must carry with him the necessary equipment for monitoring the fight scattered or insure that such is available at the installation site. In addition, he must be able to insure that it is possible to pass light across the junction at the installation site.
A particular class of connection known as hermaphroditic (or quasi-hermaphroditic) connectors, is also present in the prior art. Such connectors comprise, instead of male and female members which mate to form a connection, a pair of substantially similar or identical connector assemblies which are joined to form a complete connection. The advantage of such a connection principally resides in the elimination of differently configured members which mate to form a complete connection or coupling, inasmuch as both connector members of a hermaphroditic connection are identical. The technician or installer is not required, therefore, to anticipate whether he will require a male or a female connector member or assembly for any particular job.